673
FXUS66 KSTO 092015
AFDSTO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
115 PM PDT WED SEP 9 2026
FOR ADDITIONAL DETAILS ON WEATHER AND EXPECTED IMPACTS OVER THE
NEXT 7 DAYS, PLEASE VISIT WEATHER.GOV/STO/BRIEFING.
KEY MESSAGES
- HOT, DRY AND BREEZY THROUGH THURSDAY, WITH MODERATE TO MAJOR
HEATRISK AND ELEVATED FIRE WEATHER CONDITIONS
- SLIGHT CHANCE OF VIRGA/SPRINKLES AND SIERRA SHOWER ON
THURSDAY
- BREEZY ONSHORE WINDS THURSDAY-SATURDAY FOLLOWED BY GUSTIER
NORTH WINDS SATURDAY NIGHT-MONDAY WITH ELEVATED FIRE WEATHER
CONDITIONS
DISCUSSION
TODAY-THURSDAY:
CURRENT GOES-WEST VISIBLE SATELLITE IMAGERY ILLUSTRATES A FEW MID
TO HIGH CLOUDS CLIPPING NORTHERN CALIFORNIA WITH A FEW CUMULUS
CLOUDS OVER THE SIERRA NEVADA. CURRENT TEMPERATURES ARE TRENDING
APPROXIMATELY 5 TO 10 DEGREES WARMER THAN THIS TIME YESTERDAY
AFTERNOON. THE UPPER LEVEL PATTERN WILL FEATURE THE INFLUENCE OF
HIGH PRESSURE BRINGING HOT TEMPERATURES TO THE AREA TODAY AND
TOMORROW. THE HEAT ADVISORY REMAINS IN EFFECT THROUGH 10 PM
THURSDAY. TODAY IS EXPECTED TO BE THE HOTTEST DAY WITH MODERATE TO
LOCALLY MAJOR HEATRISK. THURSDAY WILL BE A FEW DEGREES COOLER BUT
STILL VERY HOT WITH MOSTLY MODERATE HEATRISK IN THE LOWER
ELEVATIONS. NORTHERLY FLOW TODAY AND LOW HUMIDITY WILL LEAD TO
ELEVATED FIRE WEATHER CONDITIONS FOR THE VALLEY, DELTA AND
FOOTHILLS TODAY. WINDS WILL TURN MORE ONSHORE ON THURSDAY AS RIDGE
FLATTENS, AND HUMIDITY HAS TRENDED SLIGHTLY HIGHER BUT STILL BE
LOW LEADING TO CONTINUED FIRE WEATHER CONCERNS. REMNANT TROPICAL
MOISTURE WILL MOVE INTO THE REGION OVER THE NEXT 24 HOURS OR SO,
BRINGING AN INCREASE IN PRECIPITABLE WATER (PWAT) VALUES AND
CLOUDS AT TIMES. LATEST HIGH RESOLUTION GUIDANCE IS SHOWING MAYBE
SOME ISOLATED VIRGA OR SPRINKLES THURSDAY MORNING IN THE AREA,
WITH A SLIGHT (10-15%) CHANCE OF A SHOWER IN THE SIERRA LATE
MORNING OR IN THE AFTERNOON. THERE IS A NONZERO CHANCE FOR
ISOLATED LIGHTNING IN THE SIERRA AS WELL.
FRIDAY-EARLY NEXT WEEK:
RIDGE FLATTENS BRINGING SOME COOLING TO THE AREA OVER THE WEEKEND
AND INTO NEXT WEEK, WITH GENERALLY MINOR HEATRISK FOR THE VALLEY.
TEMPERATURES WILL BE TRENDING CLOSER TO NORMAL FOR THIS TIME OF
YEAR BY FRIDAY, AND THEN BELOW NORMAL INTO NEXT WEEK. AN AREA OF
LOW PRESSURE DROPPING DOWN AND MOVING ACROSS THE PACIFIC NORTHWEST
WILL BRING INCREASED ONSHORE FLOW TO THE AREA AS WELL. BEHIND THIS
SYSTEM, INCREASED NORTHERLY FLOW LOOKS TO DEVELOP SATURDAY NIGHT
THROUGH SUNDAY. RIGHT NOW THE NATIONAL BLEND OF MODELS (NBM) SHOWS
A 30 TO 50 PERCENT CHANCE OF WIND GUSTS GREATER THAN 30 MPH ON
SUNDAY, MAINLY ALONG AND WEST OF INTERSTATE 5 IN THE SACRAMENTO
VALLEY. THIS WILL LEAD TO ANOTHER ROUND OF ELEVATED FIRE WEATHER
CONDITIONS OVER THIS TIMEFRAME. GUSTY RIDGE WINDS ARE ALSO
ANTICIPATED OVER THE WEEKEND AS THIS TROUGH SWINGS ACROSS THE
NORTHWEST. THE NBM SHOWS A 60 TO 80 PERCENT CHANCE OF WIND GUSTS
GREATER THAN 40 MPH OUT OF THE SOUTHWEST OVER THE HIGHER
ELEVATIONS OF THE SIERRA NEVADA (GENERALLY ABOVE 6000 FT) ON
SATURDAY BEFORE TURNING TO THE EAST- NORTHEAST OVERNIGHT INTO
SUNDAY, NOT QUITE AS STRONG DURING THAT PERIOD.
AVIATION
VFR CONDITIONS PREVAIL AT TAF SITES ACROSS THE FORECAST PERIOD.
BREEZY NORTH TO EAST WINDS ARE EXPECTED AT TIMES, ALTHOUGH
REMAINING 12 KTS OR LESS. SHIFT TO MORE BREEZY SOUTHERLY WINDS
AROUND 18Z THURSDAY. STRONGEST WINDS IN THE DELTA WITH GUSTS
AROUND 20 TO 25 KTS STARTING 21Z THURSDAY.
STO WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY UNTIL 10 PM PDT THURSDAY FOR BUTTE COUNTY BELOW
1000 FT-C. SAN JOAQUIN COUNTY INCLUDING STOCKTON-C. SOLANO
COUNTY INCLUDING FAIRFIELD-C. STANISLAUS COUNTY INCLUDING
MODESTO-C. YOLO/NE SOLANO INCLUDING WOODLAND-CENTRAL COLUSA
COUNTY INCL. I-5-CENTRAL GLENN CO & INTERSTATE 5-CENTRAL
MOTHERLODE 1000-3000 FT-E. DIABLO RANGE ABOVE 1000 FT-EASTERN
COLUSA COUNTY-EASTERN GLENN COUNTY-N. MOTHERLODE 1000-3000 FT-N.
SAC VALLEY IN TEHAMA COUNTY-NE SAN JOAQUIN VALLEY BELOW 1000 FT-
SW SOLANO COUNTY INCLUDING VALLEJO-SAC METRO/W. EL DORADO/AMADOR
COUNTY-SACRAMENTO COUNTY DELTA-SAN JOAQUIN COUNTY DELTA-SIERRA
(TEHAMA-PLUMAS) 1000-3000 FT-SOUTHERN MOTHERLODE 1000-3000 FT-
SUTTER/YUBA COUNTIES BELOW 1000 FT-TRACY TRIANGLE BELOW 1000 FT-
W. STANISLAUS COUNTY ABOVE 1000 FT & I-5-W. YOLO COUNTY
INCLUDING CAPAY/I-505-YOLO / SOLANO COUNTY HILLS.
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